This invention relates to furnaces and more particularly to an improved hot air furnace.
Although a wide variety of hot air furnaces are commercially available today, there is a continuing need for new and improved hot air furnaces. For example, with the recent increase in popularity of mobile homes and modular and apartment housing, there has been a great deal of interest in reducing the size of hot air furnaces while maintaining high heat capacities. However, reducing the size of conventional hot air furnaces while maintaining high heat results in several problems. One problem, for example, is durability, since as the size decreases, the high heat capacity tends to be more destructive to the structural components of the furnace.
Another problem is versatility. In mass producing large numbers of small furnaces, it becomes increasingly desirable to have such furnaces interchangeably useful with either gas or oil burners and interchangeable as to air flow direction. In mobile homes, for example, there is generally a requirement for a downward air flow while in residential homes there is generally a requirement for an upward air flow where the furnaces are often located in basements.
In some high efficiency furnaces, large flat surfaces on the heat exchanger flex during each firing of the furnace as the temperature rapidly increases, causing a loud undesirable noise generally referred to as "tin-canning". It is desirable, therefore, to design the heat exchanger to eliminate this objectionable noise.
Also, in furnaces where blower means direct air over the exterior of a flue chamber, to reduce flow resistance and, therefore, increase air flow efficiency, it is desirable to streamline the exterior of the flue chamber. Finally, heat transfer fins configurated to maximize heat transfer in the furnace while resisting wear and still being easy to manufacture are desirable.